Study on the characteristics of coal moving in sucker rod pump for CBM wells

The characteristics of coal moving in two-phase (solid+liquid) flow of sucker rod pump is related to analyze the problem of buried and card pumps and its valve leak. Based on the kinematic and dynamic analysis of coal moving with well liquid, the mathematical model of coal moving and well liquid flow was developed. The coal moving characteristics in pump was obtained on simulation analysis for different flow rate and coal diameter. The results show that the characteristics of coal moving is similar to that of well liquid flow. The positive and negative demarcation point of coal moving velocity enhances with the increase of flow rate, which will improve the coal production. The turbulence occurs at the entrance of pump, and coal is deposited in both sides of fixed valve hole due to the eddy. But two-phase (solid+liquid) flow is changed into laminar flow in the pump. The coal is deposited in the entrance of pump while the flow velocity is low or the coal diameter is large, and it results to low speed loss of coal moving. The systematic analysis of coal moving in pump of coalbed methane (CBM) wells is completed for the first time, which will provide the reasonable basis for designing sucker rod pump and operating system.